Two things that no one has brought up yet:
 
Cords:
I only had 1 ferret that ever chewed on cords, and it was only the curly
telephone cord that he showed any interest in.  The problem cured itself
the day he bit down, and it just happened to ring.
 
You probably don't want to leave a lot of cables accessable to them
however, since they will climb up them and get up on the desk, tabletop,
whatever.  They especially like computers, because of the key-clicks.  One
ferret I once had would stand on the keyboard until the buffer filled, and
it started beeping madly.  Then he would search for the tiny animal.
Another time, he danced across the keyboard, and managed to insert an
end-of-file character near the beginning of my (then) boyfriend's research
paper.  He also used to leave snuffly-sounding messages to himself on my
answering machine.
 
Cabinets:
The real danger is that there's a gap in the kick-space under your kitchen
and bathroom cabinets.  The piece of wood that you can kick with you toe is
only there for cosmetic reasons, and doesn't block off their access to the
walls.  Viewed from the side:
 
                Bottom of cabinet
 Cab.     | |      |
 door---> | |      V
          | |____________
          | |____________
          | |
          |_|     _
Kick board ----> | |         ------> god knows where this leads to
                 | |
floor____________|_|___________________
 
A series of strategically-placed bricks will cure the problem.
 
-- Anon.
 
[Posted in FML issue 0606]